The purpose of this Core is to provide a common set of state-of-the-art biochemical and genetic analyses to CIDAR researchers relevant to testing various hypotheses related to prediction of antidepressant response. The laboratories of the Core will provide assessments of hypothalamic-pituitary-adrenal (HPA) axis function, interleukin-6 and C-reactive protein (C-RP), antidepressant drug concentrations, and detailed genetic analyses. The latter includes fine mapping of candidate genes, choosing "tagging SNPs" as well as genetic data management. Particular emphasis will be placed on development of a dense polymorphism map for each candidate gene to identify the degree of linkage disequilibrium in different ethnic groups. These data will be provided to the statistical modeling core. Having these determinations performed by a central facility using a common set of high quality assay modalities will provide consistency across all of the subjects enrolled in this 5 year study.